class ActionDispatch::Routing::Mapper::Mapping

def app(blocks)
  if to.respond_to?(:action)
    Routing::RouteSet::StaticDispatcher.new to
  elsif to.respond_to?(:call)
    Constraints.new(to, blocks, Constraints::CALL)
  elsif blocks.any?
    Constraints.new(dispatcher(defaults.key?(:controller)), blocks, Constraints::SERVE)
  else
    dispatcher(defaults.key?(:controller))
  end
end